1. Field of the Invention
The present invention relates to a liquid application apparatus, a liquid application method and an image forming apparatus, and more particularly to liquid application technology that can be used desirably for depositing a treatment liquid on a recording medium prior to the deposition of an ink by means of an inkjet recording apparatus in order to promote aggregation of a color material of the ink, for example.
2. Description of the Related Art
In order to realize a high quality printing by an inkjet recording apparatus, the technology is known in which a treatment liquid, such as multivalent metal salt solution or acid aqueous solution, is deposited on a recording medium prior to depositing an ink thereon, so that the treatment liquid reacts with the ink on the recording medium so as to prevent the breeding or color mixture of the ink.
Japanese Patent Application Publication No. 2005-254809 discloses a liquid application apparatus comprising: a mechanism depositing a treatment liquid on a recording medium. The mechanism includes: an application roller serving as an application member applying the treatment liquid to the recording medium; and a liquid holding member holding the treatment liquid in a liquid holding space which is formed by causing the liquid holding member to abut against the surface (roller surface) of the application roller. According to this liquid application apparatus, by rotating the application roller, the treatment liquid held in the liquid holding space is applied to the recording medium by means of the application roller.
Here, structure of the liquid application apparatus disclosed in Japanese Patent Application Publication No. 2005-254809 is described with reference to FIGS. 13 and 14. FIG. 13 is a cross-sectional view illustrating the main structure of a general liquid application apparatus. FIG. 14 is a plan view illustrating a liquid holding member included in the liquid application apparatus illustrated in FIG. 13.
The general liquid application apparatus 900 illustrated in FIG. 13 comprises an application roller 950, a counter roller 952 opposite to the application roller 950, a liquid holding member 954 holding a treatment liquid in a liquid holding space S formed by abutting against the circumferential surface of the application roller 950.
The liquid holding member 954 is constituted by a space forming base member 955 and a circular abutment member 956 which is provided on and projects from one surface of the space forming base member 955. Further, a spring member 940 is provided on the rear side of the liquid holding member 954 so that the liquid holding member 954 is impelled toward the circumferential surface of the application roller 950 by means of the impelling force of the spring member 940. According to this structure, in a state where the abutment member 956 of the liquid holding member 954 is pressed against and abuts against (closely contact with) the circumferential surface of the application roller 950, the blocked (sealed) liquid holding space S is formed by the abutment member 956, one surface of the space forming base member 955 and the circumferential surface of the application roller 950.
Further, as illustrated in FIG. 14, in the liquid holding member 954, a liquid supply port 958 and a liquid recovery port 959 which is formed so as to pierce the space forming base member 955 are provided within the region enclosed by the abutment member 956. During performing printing (in other words, during the application operation), while a treatment liquid is supplied from a liquid supply device (not illustrated) to the liquid holding space S via the liquid supply port 958, the treatment liquid is flown out from the liquid recovery port 959, thereby performing the circulation of the treatment liquid in the liquid holding space S.
Then, by rotating the application roller 950 in a clockwise direction in terms of FIG. 13, while a recording medium 912 nipped and supported by both the rollers 950 and 952 is conveyed, the treatment liquid deposited on the circumferential surface of the application roller 950 is transferred onto the recording surface of the recording medium 912.
Further, in this liquid application apparatus 900, when it is determined that an application operation is not carried out during some time after the end of the previous application operation, the recovery operation of the treatment liquid is carried out with respect to the liquid holding space S, so that the evaporation of the application liquid (treatment liquid) in the liquid holding member 954 due to being left for a long time is reduced and the immersion of the application roller 950 into the application liquid is avoided, thereby restraining degradation of the application roller 950 caused by the application liquid.
However, in the above-described general liquid application apparatus 900, as illustrated in FIG. 15, an air bubble Q is liable to stay in the ceiling part (the upper part in the vertical direction) of the liquid holding space S when the air bubble Q enters the liquid holding space S, which may tends to develop application failure.
Further, as for the recovery operation of the treatment liquid in the liquid holding space S, as illustrated in FIG. 16, the treatment liquid tends to remain in the bottom part (the bottom part in the vertical direction) of the liquid holding space S, which may tends to develop the drying and leakage of the remaining liquid (treatment liquid).